Electrochemical Behavior of Copper Ion Complexed with Nanoparticle Organic Hybrid Materials

Abstract

Nanoscale Organic Hybrid Materials (NOHMs) have unique properties that show potential for their use as novel electrolytes that can interact with redox active species. In this work, we probe the effects of adding poly(ethyleneimine)-based NOHMs (NOHM-I-PEI) on copper ion electrochemical reactions. As NOHM-I-PEI is added to a solution containing Cu(II), the voltammetric peak current decreases. This is likely caused by strong complex formation between the PEI nitrogen and the copper, similar to complexation observed in solutions of the polymer with copper. Upon copper addition to a NOHM-I-PEI solution, the pH decreases from 10.1, plateauing at pH = 5.3 at ∼3:1 N:Cu ratio indicating that Cu(II) displaces protons. The UV-visible spectra exhibit a Cu-PEI peak, the intensity of which levels off at ∼2.8 N:Cu. Acid titration of the N-moieties of the PEI reveals three inflections corresponding to N-environments in the PEI. Upon controlling the pH of the solution by buffering, the "sequestration" of Cu(II) is found to occur when there are unprotonated nitrogens present in the NOHM-I-PEI system; this phenomenon is also supported by UV-vis results. This work highlights the potential of and the design of NOHMs to carry charged electroactive species in solutions along with key factors to control for optimal function.

Localized and Collective Dynamics in Liquid-like Polyethylenimine-Based Nanoparticle Organic Hybrid Materials

“…NOHM-I-PEI employed in this work was prepared as described in previous studies. , As briefly described, a colloidal silica suspension (7 nm diameter, Ludox SM-30 Sigma-Aldrich) was diluted to 3 wt. % and a cation exchange column (DOWEX Marathon C, Sigma-Aldrich) was employed to replace the sodium ions on the nanoparticle surface with protons.…”

“…Thus, NOHM-I-PEI-based electrolytes have been developed for combined CO 2 capture and electrochemical conversion where NOHMs can significantly increase CO 2 solubility in the electrolyte and even serve as a cocatalyst . In a recent study by some of the current authors, NOHM-I-PEI was explored as an electrolyte additive for a flow battery . This study focused on how the amine functional groups of NOHM-I-PEI can strongly chelate redox active species ( e.g., Cu­(II)) and increase the solubility of Cu in the flow battery.…”

“…29 In a recent study by some of the current authors, NOHM-I-PEI was explored as an electrolyte additive for a flow battery. 30 This study focused on how the amine functional groups of NOHM-I-PEI can strongly chelate redox active species (e. I-PEI/Cu(II) complexes as well as the effect of the pH on the extent of cation binding by NOHMs was investigated.…”

Structure and Dispersion of Free and Grafted Polymer in Nanoparticle Organic Hybrid Materials-Based Solutions by Small-Angle Neutron Scattering

“…However, commonly employed redox active materials have very limited solubilities in organic solvents. , Nonaqueous RFBs also have reduced ionic conductivity compared to aqueous RFBs, limiting achievable power densities. , Additionally, organic solvents often present undesirable safety hazards such as high volatility and flammability. Thus, emerging research has focused on the design and development of novel, structured electrolytes that can simultaneously achieve high conductivity, wide electrochemical windows, and high solubility of redox active species. − …”

“…Liquid-like nanoparticle organic hybrid materials (NOHMs) consist of a polymer canopy that is tethered to an inorganic nanoparticle core via an ionic − or covalent bond, , depending on the selection of the linker molecule. Owing to their negligible vapor pressure, improved thermal-oxidative stability relative to the neat polymer canopy, , and chemical tunability, NOHMs have been extensively studied in the neat state for various energy storage − and gas separation applications. ,,,,− More recently, this class of materials has been proposed as an emerging electrolyte additive in redox flow battery applications because of the potential for the functional groups along the polymer backbone to interact with and enhance the solubility of redox active species while maintaining high electrolyte conductivity . The electrochemical behavior of Cu­(II) ions in the presence of amine functionalized NOHMs has recently been reported .…”